Blasting cap



A. LA MOTTE.

BLASTING CAP.

APPLICATION FILED SEPT.29. 1920.

Patented Aug. 11, 1922.

lnvenfor Ar'ffiur' La M272, 7 By his 02 orney dI,

thereunder subjected to high pressure.

suntan star rear cric- ARTHUR LA MOTTE, OF WILMINGTON, DELAWARE, ASSIGNOR. TO E. I. DU PON '1 DE NEIVIOURS & COMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF.

DELAWARE.

BLASTING CAP.

To all whom it may concern Be it known that I, ARTHUR LA Morrn, a

citizen of the United States, and a resident C'f Vilmington, in the county of New Castle and State of Delaware, have invented a certain new and useful Blasting Cap, of which the following is a specification.

This invention relates to blasting caps wghich contain a secondary detonating com-- p'jpund, such as tetryl, in addition to a primg charge such as mercury fulminate.

{A preferred embodiment of my invention is} illustrated in the accompanying drawing, nihich shows a longitudinal section through the axis of a cylindrical blasting cap.

With reference tothe drawing, the cap comprises a cylinder 1, closed at the lower end, and holding therein a tightly fitting cylinder 2. The cylinder, or asIshall hereinafter designate it, reinforcing capsule, 2, is open at both ends, but is provided at its upper end with an inwardly extending flange *3, leaving but a relatively small, or restricted,

opening 4 at the upper end.

In the manufacture'of the ordinary blasting'caps of the type above described, first a secondary detonating compound and then a priming charge comprising fulminate, is in troduced into the cylinder 1, the capsule 2 inserted, and then the capsule and the chalrge he resulting cap has in the lower part 5 a 'sec ondary detonating compound such as trinitrotoluene extending up, say, to the level '6, and above that, and up to the level of the opening 4, a priming charge 7.

My invention consists chiefly in superimposing a layer of a readily ignitible material 8, extending from the flange 3 to the level 9 or to any other suitable level.

As above indicated, blasting caps have in the past been manufactured which contain a so-called secondary detonating compound, such as trinitrotoluene, picric acid, tetryl and nitrated ivory nut, all of which, however, require to be fired by a primer of mercury fulminate. In order to obtain a satisfactory blasting cap of this type, it has been necessary to use a reinforcing capsule, for unless such a capsule is used, a very large weight of a priming charge of mercury I fulminate is required, so large, in fact, that Specification of Letters Patent. Patented A 1 1922 Application filed September 29, 1920.

Serial No. 413,548.

It will be noted that the flange 3 of the capsule covers a portion of the top surface of the fulminate. This presents some disadvantages in that it offers a smaller area of fulminate to the spark or flame from the fuse. Instances have been known where safetyfuse, when out at an angle, has doubled over and prevented the spark from igmtmg the restricted area of fulminate. The present invention is designed to overcome this difficulty by superimposing a layer of a readily ignited material above the capsule in a cap of the type described.

The choice of a satisfactory material for this top layer is very wide, as any material that ignites readily and burns or explodes quickly will serve the purpose. Thus, for example, fulminate itself, guncotton, nitrostarch, nitrated ivory nut and black owder have all been used successfully in testlng my invention. It is desirable, however, if possible, to use a material which is as nonhygroscopic as possible. The most successful material of all those tried is a modified black powder in which a portion (for example, 50%) of the sulphur of ordinary black powder is replaced by antimony sulphide. Actual tests have shown that caps con taining, for instance, a base charge of nitrated ivory nut, a priming charge of mercury fulminate and potassium chlorate covered by a reinforcing capsule and an ignitingcharge of modified black powder withstood the adverse conditions of storage in damp locations for a much longer time than ordinary blasting caps composed of mercury fulminate and potassium chlorate.

It will be understood that blasting caps possessing the specially prepared ignitible surface above described may be changed in various ways without departing from my'invention, which consists essentially in providing an ign'itible surface larger then the area of the opening in the reinforcing capsule. I claim I 1. As a new article ofmanufacture, a blasting cap containing a secondary detonating compound and a priming charge at least partly enclosed by. a reinforcing capsule 2. As a new article of manufacture, a

' blasting cap containing a secondary detonating compound and a priming charge at least partly enclosed by a reinforcing capsule, said capsule having atits upper end an inwardly extending flange forming a restricted opening, and a layer of an easily 'ignitible material comprising a black powder composition covering both said flange and 0 said opening.

3. A blasting cap of the kind described in claim 1, in which the easily ignitible top layer is a modified black powder in which less than half of the sulphur has been replaced by antimony sulphide.

4. A blasting cap of the kind described in claim 1, in which the easily ignitible material above' the reinforcing capsule is also non-hygroscopic. I

. In testimony whereof I aflix my signature.

ARTHUR LA MOTTE. 

